A circle with radius $8$ has a sector with a $315^\circ$ central angle. What is the area of the sector? ${64\pi}$ $\color{#9D38BD}{315^\circ}$ ${56\pi}$ ${8}$
Answer: First, calculate the area of the whole circle. Then the area of the sector is some fraction of the whole circle's area. $A_c = \pi r^2$ $A_c = \pi (8)^2$ $A_c = 64\pi$ The ratio between the sector's central angle $\theta$ and $360^\circ$ is equal to the ratio between the sector's area, $A_s$ , and the whole circle's area, $A_c$ $\dfrac{\theta}{360^\circ} = \dfrac{A_s}{A_c}$ $\dfrac{315^\circ}{360^\circ} = \dfrac{A_s}{64\pi}$ $\dfrac{7}{8} = \dfrac{A_s}{64\pi}$ $\dfrac{7}{8} \times 64\pi = A_s$ $56\pi = A_s$